Field of the Invention
The present invention relates to a process of aromatic alkylation. More specifically, provided is a process of aromatic alkylation catalyzed by delaminated zeolites exhibiting improved reaction rates.
Description of the Related Art
Zeolites demonstrate extraordinary catalytic utility due to their well-defined catalytic active sites consisting of heteroatoms substituted within the zeolitic framework as well as shape selectivities. The crystallinity of zeolites enables high densities of uniform and well-defined acid sites, which are impossible to achieve with amorphous silica-alumina materials, and are useful as solid-acid catalysts for a number of reaction classes, including isomerization, dehydration, and alkylation. See, Corma, A. Chem. Rev. 1995, 95, 559-614; see Degnan Jr., T. F.; Smith, C. M.; Venkat, C. R. Appl. Catal., A 2001, 221, 283-294. Though sometimes all of the microporous surface area of the zeolite is available for catalysis (isomerization of 1-hexene, or alkylation of benzene with methanol to form p-xylene), in many other instances the sterics of the zeolite framework severely limits where catalysis can occur. See Gounder, R.; Iglesia, E. Acc. Chem. Res. 2011, 45, 229-238; see Gounder, R.; Iglesia, E. Chem. Commun. 2013, 49, 3491-3509; see Matias, P.; Lopes, J. M.; Laforge, S.; Magnoux, P.; Russo, P. A.; Ribeiro Carrott, M. M. L.; Guisnet, M.; Ramôa Ribeiro, F. J. Catal. 2008, 259, 190-202. Such is the case in aromatic alkylation with C3 and larger olefins, when using MWW-type zeolites such as MCM-22, which are industrial solid-acid catalysts for aromatic alkylation. Only a small fraction of the total number of acid sites is typically invoked as being active under reaction conditions in this case—those located on the external surface. See, Corma, A.; Martínez-Soria, V.; Schnoeveld, E. J. Catal. 2000, 192, 163-173; see, Millini, R. In Zeolites and Ordered Porous Solids: Fundamentals and Applications 2011; and see, Rigoreau, J.; Laforge, S.; Gnep, N. S.; Guisnet, M. J. Catal. 2005, 236, 45-54. Delamination of MWW-type layered zeolite precursors aims to synthesize catalysts with increased density of external acid sites. This leads to higher reaction rates and less deactivation for aromatic alkylation reactions. See, Corma, A.; Diaz, U.; Fornés, V.; Guil, J. M.; Martínez-Triguero, J.; Creyghton, E. J. J. Catal. 2000, 191, 218-224; see, Corma, A.; Fornés, V.; Martínez-Triguero, J.; Pergher, S. B. J. Catal. 1999, 186, 57-63; see, Corma, A.; Fornes, V.; Pergher, S. B.; Maesen, T. L. M.; Buglass, J. G. Nature 1998, 396, 353-356; and see Van Den Brink, P. J.; Corma, A.; Creyghton, E. J.; Fornés, V.; Martinez, V. Aromatics Alkylation. U.S. Pat. No. 6,855,855, Feb. 15, 2005. This has been presumed to arise from the increased external surface area of the delaminated material, as shown in FIG. 1A. In a MWW-type layered material, delamination occurs parallel to the two non-intersecting micropore channels that are used for molecular transport via diffusion, represented by the x-y plane of FIG. 1A. Because delamination is parallel to the direction of internal transport, the conventional belief has been that the benefit of delamination of MWW-type layered materials on the reaction rate is limited to only external acid-site density effects.
The industry would be well served by better understanding the catalysis of aromatic alkylation, and providing a catalytic aromatic alkylation process which has a higher reaction rate.